Dot crawling interference elimination device and color subcarrier vertical correlation detection device

ABSTRACT

A dot crawling interference elimination device and a color subcarrier vertical correlation detection device, which comprise a color subcarrier vertical correlation detection device for a video signal, an adaptive three-dimensional Y/C separation unit, and an adaptive notch filter of a color signal band, detect vertical correlation of a color subcarrier in a non-standard signal, such as a signal reproduced from a home VCRs or a special signal reproduced from an optical VDP system, that does not strictly meet the standards of the NTSC system or the PAL system, thereby to discriminate non-standard characteristics of the signal, and eliminate a color signal component, which mixes into a luminance signal when a motion-adaptive Y/C separation is carried out for the non-standard signal, by using an adaptive notch filter that suits a non-standard state of the input image signal.

BACKGROUND OF THE INVENTION

The present invention relates to a dot crawling interference eliminationdevice and a color subcarrier vertical correlation detection devicetherefor which are used to eliminate a color signal that mixes into aluminance signal when a non-standard signal which does not meet thestandards of the NTSC system or the PAL system is Y/C separated, in atelevision receiver having a motion-adaptive Y/C separation function.

There are various problems occurring in a television receiver, such asdot crawling interference and cross color interference which occur dueto multiplexing of the frequency of a color signal with the frequency ofa luminance signal, line flicker which occurs due to interlace scanning,and deterioration of picture quality which occurs due to reduction invertical resolution, etc. In order to solve these problems, framememories and digital signal processing techniques have been used inrecent years, thereby to improve the quality of the picture in atelevision receiver. These methods introduce processing techniques suchas a three dimensional Y/C separation which utilizes correlation of timedirections of video signals and a sequential scanning converter.

Based on these high picture-quality processing techniques, it is apre-condition that the input television signals are completely based onthe NTSC system or the PAL system. In other words, the signals used forthese systems have a predetermined relationship of frequencies includinga color subcarrier frequency, a horizontal scanning frequency and avertical scanning frequency (hereinafter referred to as a standardsignal). For example, in carrying out a Y/C separation of a still image,if a color subcarrier frequency, a horizontal scanning frequency and avertical scanning frequency are in a predetermined frequencyrelationship, a frame comb filter becomes valid which utilizes acorrelation of time base direction of a video signal to separate aluminance signal from a color signal. However, if a frame comb filter isused for home VCRs or personal computers which does not have apredetermined relationship of a color subcarrier frequency, a horizontalscanning frequency and a vertical scanning frequency, a Y/C separationcannot be performed normally so that this causes a problem ofdeterioration in the picture quality.

In order to solve the above problem dot crawling interferenceelimination devices have been proposed, according to which anon-standard characteristic of an input video signal is detected byutilizing inter-frame correlation of a color burst signal, and a framecomb filter and a line comb filter are changed over therebetween inaccordance with a result of the detection, and further, a notch filterfor a color subcarrier signal band is applied to a luminance signalresulting from the Y/C separation.

Description will be made of a preceding dot crawling interferenceelimination device with reference to the accompanying drawings.

FIG. 11 is a block diagram of a preceding dot crawling interferenceelimination device. In FIG. 11, 101 designates an input terminal, 102 anon-standard signal detection circuit, 103 an image motion detectioncircuit, 104 a line comb filter, 105 a frame comb filter, 106 a linecomb filter and frame comb filter change-over circuit, 107 an ORcircuit, 108 a color subcarrier band pass filter, 109 a color subcarrierband notch filter, 110 a notch filter change-over circuit, 111 asubtractor, and 112 an output terminal.

Referring to FIG. 11, when a non-standard signal is detected by thedetection circuit 102 or when a motion image is detected by thedetection circuit 103, the change-over circuit 106 selects the line combfilter 104 so that a video signal which is applied to the input terminal101 is Y/C separated by the line comb filter. When an input video signalis non-standard, the luminance signal component can not be completelyseparated from the video by the line comb filter. Therefore, theseparated luminance signal containing the color subcarrier componentattenuated by the notch filter 109 in the next step, is selected by thenotch filter change-over circuit 110 and supplied to the output terminal112.

The non-standard detection circuit 102 detects an inter-framecorrelation of the color burst signal of the input video signal, andmakes a decision whether the input signal is a non-standard signal ornot, on the basis of a result of the detection.

According to the above-described arrangement, however, a non-standardstate of an input video signal is judged based on only the inter-framecorrelation of a color burst signal. Therefore, there is a problem of anincomplete or erroneous detection of the non-standard signal when therelation between the color subcarrier frequency and the verticalscanning frequency meets the relation in a standard signal, even if thecolor subcarrier frequency does not have a normal relation with thehorizontal scanning frequency. As a result, there arises such asituation that a signal which should be Y/C separated by a line combfilter is separated by a frame comb filter. Further, there is a problemthat a color signal component which has been mixed into a luminancesignal component that is a result of such an erroneous Y/C separationprocessing, that is, a dot crawling component, does not subject to theprocessing attenuating the same by a post-stage notch filter, so that adot crawling component remains in the luminance signal component.

SUMMARY OF THE INVENTION

In light of the above-described problems, it is an object of the presentinvention to provide a dot crawling interference elimination device anda color subcarrier vertical correlation detection device used thereforwhich can extract a satisfactory luminance signal component even if therelation between a color subcarrier wave does not satisfy thepredetermined relationship of the frequencies exactly.

In order to achieve the above object, the dot crawling interferenceelimination device of the present invention comprises means fordetecting a vertical correlation from the sum of inter-line colorsubcarrier of an input video signal, and a notch filter for eliminatingdot crawling interference from a luminance signal resulting from a Y/Cseparation of the input signal, in accordance with an output of saiddetecting means.

Further, in order to achieve the above object, the color subcarriervertical correlation detection device of the present invention comprisesmeans for detecting vertical correlation of a color burst signal of aninput video signal and means for discriminating a non-standard state ofthe input video signal on the basis of an output of said detecting.

With the above-described arrangement, in a television receiver having amotion-adaptive Y/C separation function, the dot crawling interferenceelimination device of the present invention detects a verticalcorrelation of a color subcarrier of a non-standard signal which doesnot satisfy the standard of the NTSC or PAL system such as a signalreproduced from a home VCRs or an optical VDP system, and applies anotch filter to a luminance signal resulting from a Y/C separation inaccordance with a result of the detection, so that a satisfactoryluminance signal having suppressed dot crawling interferences can beobtained.

Further, in order to detect a vertical correlation of a color subcarrierof an input video signal, the color subcarrier vertical correlationdetection device of the present invention can judge a non-standard stateof the relation between the color subcarrier frequency and thehorizontal scanning frequency when the relation is non-standard, even ifthe relation between the color subcarrier frequency and the verticalscanning frequency is normal in the input video signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the configuration of a dot crawlinginterference elimination device according to one embodiment of thepresent invention;

FIG. 2 is a characteristic diagram showing one example of frequencycharacteristics of an adaptive notch filter in FIG. 1;

FIG. 3 is a block diagram showing one example of the configuration of anon-standard signal detection circuit in FIG. 1;

FIG. 4 is a waveform diagram for explaining the operation of thenon-standard signal detection circuit, in which FIG. 4-1 shows astandard state wherein the phase of a color subcarrier is invertedbetween frames, and FIG. 4-2 shows a nonstandard state wherein the phaseof the color subcarrier is in phase between the frames;

FIG. 5 is a block diagram showing one embodiment of a color subcarriervertical correlation detection device of the present invention;

FIG. 6 is a block diagram showing one example of the configuration of acolor burst signal inter-line correlation detection circuit in FIG. 5;

FIG. 7 is a waveform diagram for explaining the operation of the colorburst signal inter-line correlation detection circuit, in which FIG. 7-1shows a standard state wherein the phase of a color subcarrier isinverted between lines, and FIG. 7-2 shows a non-standard state whereinthe phase of the color subcarrier is in phase between lines;

FIG. 8, is a block diagram showing one example of the configuration of anon-standard state discrimination circuit in FIG. 5;

FIG. 9 is a waveform diagram for explaining the operation of thenon-standard state discrimination circuit;

FIG. 10 is a block diagram showing one example of the configuration ofan output control circuit in FIG. 8; and

FIG. 11 is a block diagram showing the configuration of the conventionaldot crawling interference elimination device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a block diagram of the dot crawling interference eliminationdevice of one embodiment of the present invention.

In FIG. 1, 1 designates an input terminal, 2 a frame comb filter, 3 aline comb filter, 4 a motion detection circuit, 5 a non-standard signaldetection circuit which utilizes inter-frame correlation of a colorsubcarrier, 6 an OR circuit, 7 a circuit for changing-over the line combfilter and the frame comb filter, 8 an attenuator, 9 an adaptivethree-dimensional Y/C separation circuit, 10 a vertical correlationdetection circuit for a color subcarrier, 11 a band pass filter forextracting a color subcarrier band from a luminance signal component, 12a gain control circuit for controlling an output of the band pass filter11 in accordance with an output of the color subcarrier verticalcorrelation detection circuit 10, 13 a substractor, 14 an adaptive notchfilter, and 15 an output terminal.

In the above configuration, a video signal supplied to the inputterminal 1 is supplied to the frame comb filter 2, the line comb filter3, the motion detection circuit 4, the non-standard detection circuit 5and the color subcarrier vertical correlation detection circuit 10,respectively. The motion detection circuit 4 produces an output of "1"when the input video signal is of motion picture and an output of "0"when the input video signal is of still image, and applies the signal tothe OR circuit 6. The non-standard signal detection circuit 5 detects anon-standard state of an input video signal in which a color sub-carrierwave frequency and a vertical scanning frequency do not have a normalrelation, and produces output signals of "1" and "0" when the signal isof the non-standard state and of the standard state, respectively. Thesignal is applied to the OR circuit 6. An output of the OR circuit 6controls the change-over circuit 7. In other words, when an input videosignal is of a moving picture or a input video signal is a non-standardsignal, the change-over circuit 7 selects the line comb filter 3, andthe subtractor 8 produces a luminance signal which has been Y/Cseparated by the line comb filter. When an input video signal is ofstill picture and standard signal, the frame comb filter 2 is selectedto carry out a Y/C separation. A luminance signal outputted from thesubtractor 8 passes through the color sub-carrier band pass filter 11,and the output thereof is adjusted by the gain control circuit 12. Bythe subtractor 13, output of the circuit 12 is subtracted from theluminance signal of the level before it passes the band pass filter 11,so that a dot component which is a color signal component in theluminance signal component is suppressed. A resultant output is producedfrom the output terminal 15. In this case, the attenuation quantity ofthe color signal component in the luminance signal is determined by thegain control circuit 12 which is controlled by an output from the colorsubcarrier wave vertical correlation detection circuit 10. In otherwords, characteristics of the adaptive notch filter 14 which comprisesthe color subcarrier band pass filter 11, the gain control circuit 12and the subtractor 13 change in accordance with the output of the colorsubcarrier vertical correlation detection circuit 10, as shown in FIG.2. The color subcarrier vertical correlation detection circuit 10detects inter-line correlation of a color burst signal of the inputvideo signal, detects the non-standard state in which the colorsubcarrier and a horizontal scanning frequency do not have apredetermined relation, and produces an output having a value whichcorresponds to a degree of the non-standard state. In a non-standardstate in which a color subcarrier and a horizontal scanning frequency donot have a predetermined relation, dot crawling interference occurs in aY/C separation in the configuration using a line comb filter. To avoidthis problem, gain of the above adaptive notch filter 14 is adjusted inaccordance with a non-standard state so that a luminance signal which isoptimum as a whole by having eliminated the dot interferences isproduced at the output terminal 15.

FIG. 3 is a block diagram showing one embodiment of the non-standardsignal detection circuit 5. In FIG. 3, 16 designates an input terminal,17 a one frame delay memory, 18 an adder, 19 a burst componentextraction circuit comprising a band pas filter of the color subcarrierband and a latch circuit of a burst portion, 20 an absolute valuecircuit, 21 a ripple correction circuit for selectively outputting amaximum value of adjacent three picture elements, 22 a comparator forcomparing an input signal with a predetermined reference value andoutputting "1" signal when the input signal exceeds the reference value,23 a counter circuit for counting a result of the comparison within apredetermined period, 24 an output control circuit for determining afinal output of the non-standard signal detection circuit based on aresult of the counting, and 25 an output terminal.

Operation of the circuits in FIG. 3 will be described below withreference to the waveform diagram in FIGS. 4-1 and 4-2. As shown in (a)and (c) of FIG. 4-1, when a color burst signal of a video signal appliedto the input terminal 16 is reversed in phase between a frame and thenext frame, an output of the adder 18, which is a result of the additionof the input signal and a signal which has passed through the one framedelay memory 17, becomes "0" at the burst signal portion ((e) of FIG.4-1), and remains "0" after passing through the absolute value circuit20, the ripple correction circuit 21 and the comparator 22 ((g) to (k)of FIG. 4-1). This state remains unchanged after passing through thecounter circuit 23 and the output control circuit 24, and an output fromthe output terminal 25 is also "0" signal. In this case, the input videosignal is discriminated to be of a standard state in which the colorburst signal is accurately reversed in phase between a frame and thenext frame. On the other hand, when a color burst signal of a videosignal applied to the input terminal 16 is not reversed in phase but isin phase in every one frame such as shown in (b) and (d) of FIG. 4-2,for example, an output of the absolute value circuit 20 which is asignal of the absolute value of the burst portion extracted by the burstsignal component extraction circuit 19 from the sum of the input signaland a signal that has passed through the one frame delay memory 17 ((f)of FIG. 4-2) takes a form as shown in (h) of FIG. 4-2. Further, theoutput passes through the ripple correction circuit 21 to have a ripplecomponent eliminated ((j) of FIG. 4-2) and the result thereof iscompared with a reference value in the comparator 22. As a result, " 1"signal is produced as an output as shown in (i) of FIG. 4-2.Accordingly, the result of the comparison is counted by the countercircuit 23 within a predetermined period of time, and a counted value isfurther compared with a given reference value in the output controlcircuit 24. When the counted value exceeds the reference value, a resultof the decision of a non-standard state is produced from the outputterminal 25.

Although the above embodiment shows a case where the phases of a colorburst signal are the same between the frames, it is of course possibleto detect a non standard state in a similar manner in the case where thecolor burst signal assumes an optional phase difference between frames.Further, although one frame is assumed for the capacity of the delaymemory in the above embodiment, it is of course possible to assume aninteger number of frames for the capacity of the delay memory so long asit causes the signal combination of such a phase-reversed signal of acolor subcarrier wave in accordance with the standard of an imagesignal.

FIG. 5 is a block diagram showing one embodiment of the color subcarrierwave vertical correlation detection circuit 10. In FIG. 5, 26 designatesan input terminal, 27 a color burst signal inter-line correlationdetection circuit for detecting inter-line correlation of a color burstsignal of an input video signal, 28 a non-standard state discriminationcircuit for judging or discriminating on the basis of the output of thedetection means a non-standard state in which a color subcarrier and ahorizontal scanning frequency of an input video signal are not in apredetermined relation, and 29 an output terminal.

FIG. 6 is a block diagram showing one embodiment of the color burstsignal inter-line correlation detection circuit 27 in FIG. 5. In FIG. 6,30 designates an input terminal, 31 a line delay memory, 32 an adder, 33a burst component extraction circuit, 34 an absolute value circuit, 35 aripple correction circuit, and 36 an output terminal.

Operation of the circuits in FIG. 6 will be explained below withreference to the waveform diagram in FIG. 7. As show in (a) and (c) ofFIG. 7-1, when a color burst signal of a video signal applied to theinput terminal 30 is reversed in phase between a line and the next line,an output of the adder 32, which is a result of the addition of theinput signal and a signal which has passed through the one line delaymemory 31, becomes "0" signal at the burst signal portion ((e) of FIG.7-1), and remains "0" signal after passing through the absolute valuecircuit 34 and the ripple correction circuit 35 ((g) to (i) of FIG.7-1). Accordingly, an output from the output terminal 36 also becomes"0" signal. In this case, the input video signal is discriminated to bein a standard state in which the color burst signal is accuratelyreversed in phase between a line and the next line. On the other hand,when the color burst signal of a video signal applied to the inputterminal 30 is not reveersed in phase but is in phase in every one linesuch as shown in (b) and (d) of FIG. 7-2, for example, an output of theabsolute value circuit 34 which is a signal of the absolute value of theburst portion extracted by the extraction circuit 33 from the sum of aninput signal and a signal that has passed through the one line delaymemory 31 ((f) of FIG. 7-2) takes a form as shown in (h) of FIG. 7-2.Further, the output passes through the ripple correction circuit 35 tohave a ripple component eliminated, and a waveform as shown in (j) ofFIG. 7-2 is produced as an output from the output terminal 36.

Although the above embodiment shows a case where the phases of a colorburst signal are the same between the lines, it is of course possible todetect a non-standard state in a similar manner in the case where thephases are deviated with an optional phase difference between the lines.Further, although one line is assumed for the capacity of the delaymemory in the above embodiment, it is of course possible to assume aninteger number of lines for the capacity of the delay memory so long asit causes the combination of such a phase-reversed signal of a colorsubcarrier in accordance with the standard of an image signal

FIG. 8 is a block diagram showing one embodiment of the non-standardstate decision circuit 28 in FIG. 5. In FIG. 8, 37 designates an inputterminal, 38 a comparator for comparing an input signal with apredetermined reference value and outputting "1" when the input signalexceeds the reference value, 39 a counter circuit for counting a resultof the comparison within a predetermined period, 40 an integrationcircuit for integrating an input signal within a predetermined period,41 an output control circuit for determining a final output of thenon-standard decision circuit 27 based on outputs of the counter circuit39 and the integration circuit 40, and 42 an output terminal.

In the above configuration, an inter-line correlation value of an inputcolor burst signal is applied to the comparator 38, and a result of thecomparison is applied to the counter circuit 39. The above correlationvalue is also applied to the integration circuit 40. Outputs of thecounter circuit 39 and the integration circuit 40 are simultaneouslyapplied to the output control circuit 41.

Operation of FIG. 8 will be explained below with reference to thewaveform diagram in FIG. 9.

A signal which shows an inter-line correlation value of an input colorburst signal ((a) of FIG. 9) is applied to the comparator 38 and iscompared with a predetermined reference value ((a) ref. 1 of FIG. 9).When the input value exceeds the reference value, "1" is produced, andwhen the input value does not exceed the reference value, "0" isproduced. These values are applied to the counter circuit 39. Thecounter circuit 39 counts the number of occurrence of "1" during onevertical scanning period ((b) of FIG. 9). An output of the countercircuit ((c) of FIG. 9) is applied to the output control circuit 41.This route detects mainly peak characteristics of a color burst signalinter-line correlation value.

A signal which shows an inter-line correlation value of an input colorburst signal is also applied to the integration circuit 40. In theintegration circuit 40, input signals are sequentially added in onevertical scanning period and the summation is produced as an output. Anoutput of the integration circuit ((e) of FIG. 9) is applied to theoutput control circuit 41 in a similar manner as an output of thecounter circuit is applied. This route detects mainly constantcharacteristics of a color burst signal inter-line correlation value.

The output control circuit 41 comprises a comparator 43, a D-flip-flop44, a change-over circuit 45 and an N field average circuit 46, as shownin FIG. 10, for instance. In the output control circuit 41, when aninput applied from the counter circuit 39 exceeds ref. 2 in thecomparator 43, an output from the comparator 43 becomes "1" ((d) of FIG.9). In this case, the change-over circuit 45 produces a preset maximumvalue. In other cases, the change-over circuit 45 produces an input fromthe integration circuit as it is. An output of the change-over circuit45 ((f) of FIG. 9) is averaged in an arbitrary field (N fields) period,and the result is produced.

As described above, the color subcarrier vertical correlation detectionunit in the present embodiment comprises means for detecting peakcharacteristics of a line correlation value of a color burst signal andmeans for integrating a constantly produced inter-line correlation valueof color burst signal even if it is a small value, and the unitdiscriminates a non-standard state based on the result of these twomeans, so that a non-standard state decision output having a highprecision is obtained from the output terminal 42.

Although the above-described embodiment assumes a non-standard decisioncircuit which includes both means for detecting peak characteristics ofa line correlation value of a burst signal and means for detectingconstant characteristics, it is of course effective to assume anon-standard decision circuit which uses only one of the two means.

We claim:
 1. A dot crawling interference elimination devicecomprising:means for detecting vertical correlation of a colorsubcarrier of an input video signal; Y/C separation means for separatinga luminance signal and a color signal from said input video signal inaccordance with image motion and a non-standard state of said videosignal; and an adaptive notch filter for attenuating gains of a colorsignal component in a luminance signal component separated by said Y/Cseparation means, in accordance with an output of said means fordetecting vertical correlation, wherein said means for detectingvertical correlation of a color subcarrier detects a verticalcorrelation of a color subcarrier of said input video signal andprovides an output signal representing said vertical correlation to aninput terminal of said adaptive notch filter to control said adaptivenotch filter.
 2. A dot crawling interference elimination deviceaccording to claim 1, wherein said adaptive notch filter comprises: aband pass filter for extracting a color subcarrier band from a luminancesignal component separted from said Y/C separation means; gain controlmeans for varying a gain of an output from said band pass filter inaccordance with a value of an external control signal; and a subtractorfor subtracting an output from said gain control means and a luminancesignal component.
 3. A dot crawling interference elimination deviceaccording to claim 1, wherein said Y/C separation means comprises: meansfor detecting image motion of said input video signal; means fordetecting non-standard characteristics on the basis of a framecorrelation of a color subcarrier of said video signal; a line combfilter; a frame comb filter; and change-over means for changing overbetween said line comb filter and said frame comb filter in accordancewith a detected output from said motion detection means or, saidnon-standard detection means.
 4. A dot crawling interference eliminationdevice comprising:means for detecting vertical correlation of a colorsubcarrier of an input video signal; Y/C separation means for separatinga luminance signal and a color signal from said input video signal inaccordance with image motion and a non-standard state of said videosignal; and an adaptive notch filter for attenuating gains of a colorsignal component in a luminance signal component separated by said Y/Cseparation means, in accordance with an output of said means fordetecting vertical correlation, said Y/C separation means comprising:means for detecting image motion of said video signal; means fordetecting non-standard characteristics on the basis of a framecorrelation of a color subcarrier of said video signal; a line combfilter; a frame comb filter; and change-over means for changing overbetween said line comb filter and said frame comb filter in accordancewith a detected output from said motion detection means or saidnon-standard detection means, and said non-standard detection meansincluding: arithmetic means for making a sum of color burst signals froman input video signal between frames; detection means for detecting anamplitude of a color burst signal portion from an output of saidarithmetic means and detecting a frame correlation of the color burstsignal; comparator means for comparing an output of said detection meanswith a predetermined reference value; counter means for counting anumber of times when said frame correlation value becomes higher thansaid reference value within a predetermined period; and output controlmeans for controlling an output on the basis of the value of an outputfrom said counter means.
 5. A color subcarrier correlation detectiondevice, comprising:color burst signal line correlation detection meansfor detecting a correlation of a color burst signal of an input videosignal between lines; and non-standard state decision means fordiscriminating a non-standard state in which a color subcarrier and ahorizontal scanning frequency are not in a predetermined relationship,based on said detection means, said non-standard state decision meansincluding: comparison means for comparing a line correlation valuedetected by said detection means with a predetermined reference value;counter means for counting a number of times when said line correlationvalue becomes equal to or higher than said reference value, within apredetermined period; and output control means for controlling an outputon the basis of the value of an output from said counter means.
 6. Acolor subcarrier vertical correlation detection device comprising:colorburst signal line correlation detection means for detecting acorrelation of a color burst signal of an input video signal betweenlines; and non-standard state decision means for discriminating anon-standard state in which a color subcarrier and a horizontal scanningfrequency are not in a predetermined relationship, based on saiddetection means, said non-standard state decision means including:integration means for integrating a line correlation value of the inputcolor burst signal within a vertical scanning period; and output controlmeans for controlling an output on the basis of the value of an outputof said integration means.
 7. A color subcarrier vertical correlationdetection device comprising:color burst signal line correlationdetection means for detecting a correlation of a color burst signal ofan input video signal between lines; and non-standard state decisionmeans for discriminating a non-standard state in which a colorsubcarrier and a horizontal scanning frequency are not in apredetermined relationship, based on said detection means, saidnon-standard state decision means including: comparison means forcomparing a line correlation value of the input color burst signal witha predetermined reference value; counter means for counting a number oftimes when said line correlation value becomes higher than saidreference value, within a predetermined period; integration means forintegrating a line correlation value of the input color burst signalwithin a vertical scanning period; and an output control means forcontrolling an output on the basis of a value which is a result ofmixing of an output value of said counter means and an output value ofsaid integration means.